1. Field of the Invention
This invention relates to an automatic time-base error correction system and in particular to an automatic time-base error correction system using a pair of random access memories.
2. Description of the Prior Art
Magnetic tape recorders, particularly video tape recorders, can yield distortions because of time-base errors in reproducing signals therefrom. These errors arise from various factors such as tape speed variations caused by high frequency components of flutter, tape expansion, variations of magnetic head rotation speed, and so on.
It is well known that the error can be corrected by using a variable delay line with feedback control. This method, however, is incapable of perfectly removing the time-base error in the input signal because of use of feedback control.
There is also known a system for correcting the time-base errors by using three or more shift-registers. According to this system, the output signal from shift-registers is read out at a uniform rate so that the time-base error can be corrected. The problem with this system is poor transfer efficiency in shift-registers, resulting in reduced level of output signal. Also, according to this system, the input signal is stored in portions corresponding to the bit number of each shift-register, so that if a large time-base error is included in the input signal, such error can not be corrected. Further, as shift-registers are used in large number, the control circuit is complicated.